The scientific importance of Dr. Eugène Leloup, one of the key biologists of the Royal Belgian Institute of Natural Sciences in the past century, is documented through his scientific output. We overviewed the scientific career of Dr. E. Leloup by listing his publications, the taxa introduced therein and, when possible, their taxonomic and nomenclatural status as well as their physical whereabouts. An annotated list of his eponyms is also provided.